The invention relates to permanent tissue markings that can be changed or removed, or both, on demand.
Tattoos have been used in almost every culture throughout history. They have been found on a five thousand year old human mummy, and decorated figurines suggest their use at least fifteen thousand years ago. Tattoos have been used for many purposes including identity, beauty, artistic and spiritual expression, medicine, and magic.
In the United States, statistics are not kept on tattooing but the practice has apparently been growing in popularity for the past few decades. The majority of tattoos are apparently obtained by people under forty years of age, including a significant proportion of teenagers. An estimated 2 million people are tattooed every year.
In the U.S. today, the uses of tattooing have expanded to include not only the familiar artistic tattoo, but also permanent makeup, for example, permanent eyebrows, eyeliner, lip liner, and lip color; corrective or reconstructive pigmentation, for example, repigmentation of scar tissue or areola reconstruction on mastectomy patients; medical markings, for example, marking gastrointestinal surgery sites for future monitoring; and identification markings on animals, for example, pedigree xe2x80x9ctagsxe2x80x9d on purebred pets.
The tattooing procedure consists of piercing the skin with needles or similar instruments to introduce an ink that includes small particles of pigment suspended in a liquid carrier. During the healing process, some particles of pigment are sloughed from the skin surface and others are transported to the lymphatic system. What one sees as the tattoo are the remaining particles of pigment located in the dermis where they are engulfed by phagocytic skin cells (such as fibroblasts and macrophages) or are retained in the extracellular matrix.
To create a permanent tattoo one must implant pigments that are not dissolved or digested by living tissue. Primitive pigments probably consisted of graphite and other carbon substances. Modern pigments also include inorganic metal salts and brightly colored organometallic complexes.
Tattoo ink ingredients have never yet been regulated or fully disclosed to the public. Ink composition and pigment sources remain trade secrets. Allergic reactions to these unknown and/or undisclosed substances, rare but in some cases severe, have been reported at the time of tattooing, well after the time of tattooing, and after exposure to sunlight or laser treatments.
The long-term health effects, including potential toxicity and/or carcinogenicity of tattoo pigments, have not been studied and are not known. Unfortunately, these pigments, chosen for their permanence, are believed to remain in the body for life, concentrated in the lymph nodes, even if the visible tattoo is xe2x80x9cremovedxe2x80x9d from the marked area, for example, by laser treatment.
A widely recognized problem with tattoos is that they cannot be easily removed. One survey indicated that about half of all Americans with tattoos at some point wish they could remove them. Dissatisfaction can stem from undesired social disapproval; from the appearance of a tattoo that may be poorly executed, out-of-style, or inaccurate (commonly in the case of name-containing vow tattoos); or from changes in the wearer""s self-perception or lifestyle, which are especially likely for the increasing number of young customers.
Tattoo xe2x80x9cremovalxe2x80x9d methods have included overtattooing without ink, dermabrasion, and surgical excision, all of which usually leave unacceptable appearance and/or scarring. The use of these removal methods was recorded as early as the first century A.D. in Rome, when soldiers returned from barbaric regions with tattoos that were unacceptable to society.
In fact, there had been no significant technological advances in tattoo removal methods until the 1960s when Dr. Leon Goldman pioneered the use of pulsed lasers. This method was improved in the 1980s by Dr. R. Rox Anderson, and has since become widely practiced. Removal can now also be achieved using variable-wavelength intense pulsed light sources (flash-lamps).
Ideally, short, powerful light pulses are absorbed specifically by tattoo pigment particles with little or no absorption by surrounding tissue, thereby causing the particles of pigment to break apart with minimal damage to neighboring skin structures. Skin injury is extremely local and scarring is uncommon. Instantaneously, some particles of pigment are apparently broken into pieces which have far less optical absorption than the original particles, and thus are less visible. During the healing process, many particles are physically removed from the tattoo site while others remain in the dermis as a residual tattoo.
Despite advantages over older methods, laser or flash-lamp removal of standard tattoos is not ideal. A treatment course requires an average of approximately eight laser treatments at a cost of several hundred dollars apiece. The treatments must be spaced at least one month apart and can be painful. Because a laser must be chosen for absorption of its emission wavelength by the particular pigment, multiple lasers are needed to treat multicolored tattoos effectively; however, a removal practitioner""s office may not offer the optimal laser(s) to treat a specific tattoo. Certain pigments, including many greens, remain difficult to remove, and there is currently no commercially available tattoo removal laser which effectively treats most yellow pigments. Intense visible light sometimes targets the skin""s natural epidermal pigment, melanin, resulting in temporary or permanent hypo- or hyperpigmentation, especially in dark or tanned skin, and/or hair loss in the area. In addition, some tattoo pigments undergo color changes in response to treatment. For example, inks used for permanent makeup often contain certain iron, titanium, or other oxides which are irreversibly blackened upon exposure to Q-switched lasers, and cannot always be removed by further treatments.
After the treatment course, most patients can expect that a tattoo will not be prominently visible or recognizable, but it is unusual to be able to restore the skin to its original pre-tattoo appearance. Because of the numerous drawbacks, only a fraction of those people who are unhappy with their tattoos pursue tattoo removal.
The invention provides for permanent markings (such as tattoos) in tissue (typically living tissue, such as skin) that are designed in advance to be easily changed and/or removed on demand. These markings are created using indispersible microparticles that consist of or contain chromophores. These microparticles are designed in advance with one or more specific properties (such as electromagnetic and/or structural properties) that allow the microparticles to be altered by exposure to a specific energy (such as a specific electromagnetic radiation) to change and/or remove the tissue markings.
In general, the invention features a method of applying to a tissue a detectable marking that can be changed or removed, or both, on demand, by obtaining colored microparticles each including a chromophore and having a specific property that is designed in advance to enable the microparticles to be altered when exposed to a specific energy (for example, electromagnetic radiation such as near-infrared (near-IR), infrared (IR), near-ultra violet (near-UV), or high intensity visible radiation); and implanting into the tissue a sufficient number of the colored microparticles to form a detectable tissue marking, wherein the tissue marking is permanent until the specific energy is applied to alter the microparticles to change or remove, or both, the detectable marking. In this method, the chromophore or an additional material can provide the specific property, which can be, for example, the absorption of the specific energy, photochemical reactivity, or thermochemical reactivity when the microparticles are exposed to the specific energy. The specific energy can be applied only once to change or remove, or both, the detectable marking.
In certain embodiments, the colored microparticles each include (i) an indispersible, biologically inert coating, (ii) a core enveloped within the coating, wherein the core includes the chromophore which is detectable through the coating and is dispersible in the tissue upon release from the microparticle, and, optionally (iii) an absorption component that absorbs the specific energy and that is located in the coating or the core, or both; and the specific property is the absorption of the specific energy to rupture the microparticle, releasing the chromophore which disperses in the tissue, thereby changing or removing, or both, the detectable marking, wherein the coating, the core, or the optional absorption component, or any combination thereof, provide the specific property.
For example, the dispersible chromophore can be dissolved or metabolized when released into the tissue, or the chromophore can be insoluble and have a size and configuration such that it is physically relocated from the detectable marking by biological processes when released into the tissue. The chromophore can be or include rifampin, xcex2-carotene, tetracycline, indocyanine green, Evan""s blue, methylene blue, FDandC Blue No. 1 (Brilliant Blue FCF), FDandC Green No. 3 (Fast Green FCF), FDandC Red No. 3 (Erythrosine), FDandC Red No. 40, FDandC Yellow No. 5 (Tartrazine), or FDandC Yellow No. 6 (Sunset Yellow FCF). The chromophore can be any colored substance approved by the United States Food and Drug Administration for use in humans. In certain embodiments, the chromophore can be detected by the naked eye under normal lighting conditions or when exposed to UV, near-UV, IR, or near-IR radiation.
In other embodiments, the coating, the chromophore, or the optional absorption component, or any combination thereof, absorb specific electromagnetic radiation. The coating can be made of or include a metal oxide, silica, glass, fluorocarbon resin, organic polymer, wax, or a combination thereof. The coating can be substantially visibly transparent and absorb near-IR radiation, for example, at a wavelength between about 750 nm and about 2000 nm. The absorption component can be or include Schott filter glass, graphite, carbon, a metal oxide, an acrylate polymer, or a urethane polymer. The coating can itself absorb, or include an absorption component that absorbs, near-IR, IR, near-UV, or high intensity visible radiation.
In another embodiment, the coating can include pores of a size sufficient to allow the dispersible chromophore to leach out of the microparticle, for example, over a period of weeks or months, so that the tissue marking disappears at a given time. This provides tissue markings that fade slowly after microparticle implantation. These markings can also be removed at once upon exposure to the specific energy. The microparticles can also include multiple cores enveloped within one coating.
The invention also features a method in which the colored microparticles each include (i) an indispersible, biologically inert coating, (ii) a core enveloped within the coating, wherein the core includes the chromophore which is detectable through the coating and is altered upon exposure of the microparticle to the specific energy (such as near-infrared or infrared radiation), and optionally (iii) an absorption component that absorbs the specific energy and that is located in the coating or the core, or both; and in which the specific property is the ability of the chromophore to be altered upon exposure of the microparticle to the specific energy, thereby changing or removing, or both, the detectable marking, wherein the coating, the core, or the optional absorption component, or any combination thereof, provide the specific property. In this embodiment, the chromophores need not be dispersible, and the microparticles are not necessarily ruptured.
For example, the chromophore can be altered by losing its color or by changing from an initial color to a different color upon exposure to the specific energy. The microparticle can further include a sub-microparticle that includes a bleaching agent that is released from the sub-microparticle upon exposure of the microparticle to the specific energy, thereby bleaching the chromophore (for example, rendering it substantially invisible). The bleaching agent can be a peroxide, hypochlorite, excited oxygen species, or free radical. The chromophore can be pH-sensitive, and the bleaching agent is an acid, a base, or a buffer capable of effecting a pH transition within the core that bleaches the chromophore.
The photobleachable chromophore can be Rose Bengal, rhodamine compounds, coumarin compounds, dye-paired ion compounds, cationic dye-borate anion complexes, or bis(diiminosuccino-nitrilo)metal complexes. The chromophore can also be thermolabile, and exposure of the microparticle to the specific energy heats and alters the chromophore. In this method, the absorption component can be Schott filter glass, graphite, carbon, a metal oxide, an acrylate polymer, or a urethane polymer.
The methods can be used to mark a variety of tissues including skin, iris, sclera, dentin, fingernails, toenails, tissue beneath fingernails, tissue beneath toenails, tissue inside the mouth, and tissue lining internal body passages. In these methods, the specific energy can be applied at a wavelength, at an intensity, or for a duration, or any combination thereof, insufficient to completely remove or change the detectable marking, thereby partially removing or changing, or both, the detectable marking. The specific energy can be applied only once to effect the rupture or alteration.
In another aspect, the invention features a method of changing or removing, or both, a detectable marking created by implanting into tissue a sufficient number of colored microparticles each comprising a chromophore and having a specific property that is designed in advance to enable the microparticles to be altered when exposed to a specific energy, by exposing the detectable marking to the specific energy for a time sufficient to alter the microparticles, thereby changing or removing, or both, the detectable tissue marking. In this method, the microparticles are altered to become substantially undetectable, thereby removing the tissue marking, for example, by rupturing and releasing the chromophore, or by losing the color of the chromophore. Alternatively, the microparticles can be altered by changing from an initial color to a different color, thereby changing the color of the tissue marking. In this method, the colored microparticles can be those described herein.
In yet another aspect, the invention features colored microparticles that includes (i) an indispersible, biologically inert coating that provides from about 10 to about 95 percent of the volume (such as 15 to 25 or 35 percent) of the microparticle (and that renders the chromophores less dispersible or indispersible), (ii) a core enveloped within the coating, wherein the core is or includes a chromophore that is detectable through the coating and is dispersible in living tissue upon release from the microparticle, and, optionally (iii) an absorption component that absorbs a specific energy (such as near-infrared or infrared radiation) and that is located in the coating or the core, or both; wherein the coating, the core, or the optional absorption component, or any combination thereof, is designed in advance to absorb the specific energy to rupture the microparticle, releasing the chromophore which disperses in the living tissue.
In another aspect the invention features a colored microparticle that includes (i) an indispersible, biologically inert coating comprising from about 10 to about 95 percent of the volume of the microparticle (such as 40 or 50 to 80 or 90 percent), (ii) a core enveloped within the coating, wherein the core is or includes a chromophore that is detectable through the coating and is altered upon exposure of the microparticle to a specific energy (such as near-infrared, infrared, ultraviolet, or high-intensity visible radiation), and optionally (iii) an absorption component that absorbs the specific energy and that is located in the coating or the core, or both; wherein the coating, the core, or the optional absorption component, or any combination thereof, is designed in advance to absorb the specific energy to alter the chromophore.
These microparticles can have a radius of from 50 nanometers to 100 microns. The coating can be or include a metal oxide, silica, glass, fluorocarbon resin, organic polymer, wax, or any combination thereof. In certain embodiments of the rupturable microparticles, the absorption component forms a plug sealing a hole in the coating, wherein the plug is destroyed upon exposure to the specific energy to open the hole in the coating. Alternatively, the coating can include one or more absorption components that when exposed to the specific energy cause the coating to break open. The colored microparticles can be sterilized.
The colored microparticles (preferably the microparticles with a non-rupturing outer coating) can further include a sub-microparticle (that can have its own coating), for example, in the core, that includes a bleaching agent (such as a peroxide, hypochlorite, excited oxygen species, or free radical) that is released from the sub-microparticle upon exposure of the microparticle to the specific energy, thereby bleaching the chromophore. The chromophore can be photobleachable, and exposure of the microparticle to the specific energy renders the chromophore substantially invisible. The chromophore can be thermolabile, and exposure of the microparticle to the specific energy renders the chromophore substantially undetectable or invisible.
The invention also features tissue marking inks that include the colored microparticles and a liquid carrier, which can include alcohol, water, or glycerin, or any combination thereof.
Additional embodiments are possible wherein the microparticles do not necessarily include a coating or encapsulation, and the microparticles are designed in advance with strong absorption of specific energy which renders the chromophores (1) dispersible from the microparticles or (2) invisible.
A significant feature of composite microparticles, especially such as those that are ruptured, is that a common property (such as a specific electromagnetic absorption peak) can be included in diverse microparticles (having multiple colors). These diverse microparticles can include a common material (in composite constructions) or materials with similar absorption spectra. For example, this design allows removal of multiple colors in a tissue marking through common treatment with a specific type of energy (such as one wavelength emitted by one existing laser).
As used herein, a xe2x80x9cmicroparticlexe2x80x9d is a particle of a relatively small size, not necessarily in the micron size range; the term is used in reference to particles of sizes that can be implanted to form tissue markings and thus can be less than 50 nm to 100 microns or greater. In contrast, a xe2x80x9cnanoparticlexe2x80x9d is specifically a particle in the nanometer (10xe2x88x929) size range, for example, 15 nm or 500 nm. A micro- or nanoparticle may be of composite construction and is not necessarily a pure substance; it may be spherical or any other shape.
As used herein, a xe2x80x9cdispersiblexe2x80x9d substance (such as a chromophore) is (1) dissolved by (and is soluble in) bodily fluids, for example, those within a cell or tissue; (2) metabolized (including digested) by living tissue and/or cells into one or more new chemical products; and/or (3) of a size (on average no larger than about 50 nanometers, but in some cases necessarily much smaller, for example, less than about 5 nm) made of a material, and configured such that normal bodily processes result in its physical relocation from tissue (from cells or from extracellular matrix).
As used herein, an xe2x80x9cindispersiblexe2x80x9d substance (such as a coating material or an individual microparticle) does not disintegrate, dissolve, or become metabolized in tissue. xe2x80x9cIndispersiblexe2x80x9d microparticles are also large enough on average (generally greater than about 50 nm, but depending on the material as small as 5 nm or even smaller) and have a configuration on average such that when a plurality is implanted into tissue a sufficient number is retained to form a detectable marking, even though some number of the individual microparticles may be relocated from the tissue marking site through biological processes (such as lymphatic transport).
An xe2x80x9cinertxe2x80x9d or xe2x80x9cbiologically inertxe2x80x9d substance (such as the coating material of a microparticle) generally creates no significant biochemical, allergic, or immune response after the normal healing period when implanted into living tissue.
A xe2x80x9cchromophorexe2x80x9d is broadly defined herein as a substance (solid, liquid, or gas) that has color or imparts a color to the intact microparticles (including when the substance itself lacks color, for example, a clear gas, but scatters electromagnetic waves, for example, light, and thus may appear colored, for example, white, blue, green, or yellow, depending on its scattering properties) under some conditions, for example, all of the time or after exposure to a certain wavelength (such as in a fluorescent substance). For example, a chromophore can be a fluorescent, phosphorescent, wavelength up-converting, or other substance that may normally be substantially invisible, but that emits ultraviolet, visible, or infrared wavelengths during and/or after exposure to wavelengths from a particular region of the electromagnetic spectrum. A chromophore can also be a substance that reversibly or irreversibly changes color spontaneously or in response to any stimulus.
xe2x80x9cColorxe2x80x9d is broadly defined herein as a detectable (that is, visible or able to be made visible under certain lighting conditions, or able to be detected using a device, for example, an infrared camera) property determined by a substance""s electromagnetic absorption and/or emission spectrum (that is, in the ultraviolet, near-ultraviolet, visible, near-infrared, infrared, and other ranges). Black and white are colors under this definition.
As used herein, a substance (such as a chromophore) is xe2x80x9cinvisiblexe2x80x9d when essentially no color can be detected (such as in a tissue marking site) apart from the normal coloration of the substance""s surroundings (such as skin or other tissue) by the naked eye under normal lighting conditions, for example, diffuse sunlight or standard artificial lighting. A substance is xe2x80x9cundetectablexe2x80x9d when it is invisible to the naked eye under normal lighting conditions, and also invisible by the naked eye, or a device, under any other lighting conditions (such as fluorescent, UV, or near-infrared).
As used herein, a xe2x80x9cpermanent tissue markingxe2x80x9d or xe2x80x9ctissue markingxe2x80x9d is any mark created by the introduction of microparticles of the invention into tissue, typically living tissue, with the intention of permanent or long-term endurance. Markings can be any color and must be detectable, for example, by the naked eye or by an infrared detection device, when exposed to electromagnetic radiation in one or more regions of the spectrum, for example, the visible or near-infrared regions. A permanent marking is generally a marking that remains visible or otherwise detectable until it is exposed to a specific energy. However, in certain embodiments, a permanent marking can be a mark that is designed in advance to disappear after a predetermined time, for example after one or several months, and/or can be removed by exposure to a specific energy before the predetermined time.
As used herein, a xe2x80x9ctattooxe2x80x9d is a type of tissue marking wherein the tissue is usually skin. xe2x80x9cStandard tattoosxe2x80x9d and the pigments used to create them have not been designed in advance for change and/or removal.
As used herein, a xe2x80x9cnon-invasivexe2x80x9d procedure for creating a tissue marking implants microparticles into the tissue without the use of an implement that enters the surface of the tissue. Forces that can be applied to microparticles to achieve non-invasive tattooing include ballistic, electrical (such as through iontophoresis or electroporation) magnetic, electromagnetic, ultrasonic, chemical, and chemical gradient forces, or any combination of these forces.
As used herein, xe2x80x9cremovalxe2x80x9d of a tissue marking means either the physical removal of the substance(s) that create the appearance of the marking, or the destruction or facilitated loss of some chromophoric property that renders the marking invisible. Thus, all, some, or none of the components (chromophores, coating material, etc.) of the microparticles may be physically relocated from the tissue when a tissue marking is xe2x80x9cremoved.xe2x80x9d
Tissue marking microparticles that are xe2x80x9cdesigned in advancexe2x80x9d for change and/or removal means that the materials and/or structure of the microparticles are selected and/or engineered, and intended, to facilitate change and/or removal of the tissue marking. It in no way implies that a predetermined removal method must be used, that this or another removal method is the best method, or that a removal method is explicitly outlined at the time of microparticle design. Multiple removal methods may be acceptable for removing a given marking. Adjustments made to any proposed method may affect removal efficacy positively, negatively, or not at all.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be limiting.
The invention provides several advantages over standard tattoos and their removal. Standard tattoos are made using unregulated pigments of undisclosed nature which, once implanted, are in direct contact with living tissue for the recipient""s life, even if no longer visible at the tissue marking site. A course of many treatments to remove a standard tattoo is not always successful, yet it is time-consuming and expensive, may expose the tissue to a damaging amount of radiation, requires guesswork and experimentation on the part of the practitioner, and, in the case of multicolored tattoos, may require multiple lasers.
Through practice of the methods disclosed herein, tissue marking removal treatments can become essentially 100% effective. The associated costs of removal in terms of time (such as length of treatment course) and/or money can be reduced compared to standard tattoo removal treatment.
By using tissue markings specifically designed in advance for removal, the invention can reduce the total dose of energy (such as laser radiation) to which the tissue marking site must be exposed for removal. The incidence of patient pain and complications including skin injury can be reduced compared to treatments to remove standard tattoos, which can include more irradiation sessions at higher fluences.
In addition, the parameters (such as fluence and pulse duration) for removal of tissue markings of the invention can be optimized in controlled studies. When provided to practitioners, guesswork and experimentation can be eliminated from treatments to remove tissue markings of the invention and treatment outcome will be predictable.
Whereas removal of standard multicolored tattoos requires treatment with multiple laser wavelengths absorbed by different pigments, microparticles of the invention can be constructed such that one type of energy (such as one wavelength) can target diverse microparticles. One benefit of this feature, if multicolored microparticles are designed in advance for removal by a single wavelength, is that removal practitioners will need only one device to treat all patients for removal of tissue markings of the invention. Currently, practitioners do not always have all of the lasers needed for optimal treatment of standard multicolored tattoos, in part because tattoo removal devices are expensive (approximately $30,000 for a 3 Joule, Q-switched ruby laser to about $100,000 for a flash-lamp).
In addition, the invention can reduce short- and long-term health risks associated with standard tattoo pigments. Microparticles of the invention can be designed to be inert and non-toxic when implanted in tissue and/or can be constructed using materials that are already accepted for long-term use in the human body.
According to important embodiments of the invention, chromophores are encapsulated in inert materials to provide the microparticles for tissue marking. These chromophores have minimal direct contact with the recipient""s body; whereas, in standard tattoos, the chromophoric pigments are directly in contact with the body in tissue cells and are thought to be stored in the lymph nodes for life.
Furthermore, the composition of tissue marking inks made with the new microparticles will be known and can be disclosed in advance to allow those with recognized allergies to avoid implantation and to provide critical information for treating reactions.
Other features and advantages of the invention are apparent from the following detailed description and from the claims.